Control device with snap switch

ABSTRACT

The invention relates to a control device of the type including a movable impulse member which is responsive to predetermined values and acts against a plate spring member, and takes one or the other of two positions, said plate spring member, which is kept under tensional stress, having a lever arm at one location and being acted upon by said impulse member at another location and being devised to impart to said arm a deflection reaching a considerable angle at one position of said impulse member but an insignificant deflection only in the other position of said impulse member.

[451 Aug. 20, 1974 CONTROL DEVICE WITH SNAP SWITCH [75] Inventor:

Stockholm, Sweden [73] Assignee: Sixten Englesson Teknisk Konsiil t AB, Solna, Sweden; a part interest [22] Filed: Apr. 13, 1970 [21] Appl. No.: 27,693

[52] US. Cl. 200/67 DA, 200/83 P, 200/83 1 [51] Int. Cl. H0lh 21/04 [58] Field of Search 200/83 P, 83 J, 67 DA, 200/67 DB [56] References Cited UNITED STATES PATENTS 2,647,968 8/1953 Byam H ZOO/83 P 2,766,350 10/1956 Gres et al. 200/83 P 2,899,512 8/1959 Burch. 200/62 DA Kadisevskis 200/67 DA Carlstedt 200/83 J UX Primary Examiner-Robert K. Schaefer Assistant Examiner--Gerald P. Tolin [5 7] ABSTRACT The invention relates to a control device of the type including a movable impulse member which is responsive to predetermined values and acts against a plate spring member, and takes one or the other of two positions, said plate spring member, which is kept under tensional stress, having a lever arm at one location and being acted upon by said impulse member at another location and being devised to impart to said arm a deflection reaching a considerable angle at one position of said impulse member but an insignificant deflection only in the other position of said impulse member.

1" CH1 '3 Drawing Figures simmer} PATENTED AUG 2 0 I974 CONTROL DEVICE WITH SNAP SWITCH SUMMARY AND BACKGROUND OF THE INVENTION This invention relates to a control device which is provided with a movable impulse member, which, in response, for instance, to the value of a unit such as the pressure prevailing in a gas or a liquid, takes one or the other of two positions against the action of a plate spring, the spring pressure being constant in the one position and variable in the other position. As an example of a field of utilization to which the invention is applicable there may be mentioned drainage pumps which are started automatically when the level in a collection of water, e.g. a cesspool or sink reaches a predetermined high value, and are stopped also automatically when the level has fallen to a predetermined low value. The higher level can be varied from case to case and therefore the spring pressure is adjustable in the mentioned second position so as to cause the spring to become deflected in accordance with the water level under consideration. Control devices of this kind are known per se, e.g. from the Swedish patent No. 215,266.

It is one main object of the invention to provide a control device within which the spring is capable of op erating within a greater interval and under surer and more exact conditions than in the known embodiment.

This is substantially obtained by clamping the plate spring member, which in a manner known per se is in almost plane condition under tensile stress at two ends and by providing at one place with a lever arm, said impulse member being disposed to act on the spring member at another place, said plate spring member further being devised to impart to said lever arm a deflection which in said second position is through a considerable angle and which in said first-mentioned position is insignificant or nil. The plate spring member is in its principal shape known in connection with switches, in which connection it however is always the intention that its arm is to take one or the other of its two contact positions under the action of substantially one and the same force. According to the invention, however, there is provided a substantially constant holding force in one position of the spring arm and a continuously adjustable action force in the other position thereof.

Further objects and advantages of the invention will become apparent from the following description, considered in connection with the accompanying drawings illustrating one embodiment of the invention by way of example and forming part of its specification.

THE DRAWINGS In the drawings.

FIG. I is a perspective and partially sectional view of the control device or pressure relay embodying the features of the invention;

FIG. 2 is a vertical projection of the plate spring and FIG. 3 a lateral view thereof, both views being in a larger scale than that of FIG. 1

DESCRIPT ION The pressure relay shown in the drawing has a casing formed in two parts 10, 12 which are interconnected e. g. by means of screws not shown. The part 10 may be of metal, whereas the part 12 suitably is made of some plastic material or other electricity non-conductive material. A disc 14, a member 16 and a sealing ring 18 are in a tightening manner clamped between said parts. The membrane 16 forms one lateral wall of a chamber 20 which through a pipe socket 22 is connectable to a conduit not shown an extending to the fluid, the level of which is to be controlled, such as that of the water in a sink or the like. The circular member 16 is of some resilient material and under the action of the pressure of a fluid is caused to bend outwards to a greater or lesser degree. Provided on the rear side of the membrane 16 is a circular support member 24 which has a smaller diameter than the membrane and which with a small clearance fits into a chamber 26 formed by the disc 14. When the pressure in the fluid has reached a predetermined value, the membrane 16 will abut against the disc 14 outside of the chamber 26 which results in the free area of the membrane being reduced in corresponsponse to said reduction of the free area of the membrane, as is easily understood.

The support member 24 is at its center connected with a guide 28 which is displaceably located in a bush ing 30 inserted into the disc 14. The guide 28 merges into a pin 32 having a highly reduced cross-sectional area. The guide 28 is suitably untrue, such as square. Further the pin 32 travels with some clearance within the bushing so that the chamber 26 is in communication with the chamber 34 between the portion 12 of the casing and the disc 14.

A plate spring generally denoted 36 has at its ends annular openings 38, 40 by means of which it is clamped in a plane frame 42 rigidly secured to the portion 12 of the casing. Said frame is provided with two support projections 44, 46 having plane surfaces 45 and 47, respectively (FIG. 3) with which the ends of the plate spring are in tight contact. Inserted into the openings 38, 40 and apertures in the frame are screw joints 48, 50. The screw joint 50 has an excentric portion 52 fitting to the opening 40 whereby the spring 36 can be stressed between the screw joints 48, S0 with any desired tensional force.

The plate spring 36 is made with a double loop or bend and thereby given a kind of S-shape in a manner known per se. The one loop or bend 54 extends in one direction outwardly away from a line 56 connecting the central points of the openings 38, 40 and the other loop or bend 58 extends in the opposite direction. The loop or bend 58 extends for a greater distance from the line 56 than the loop or bend 54. Further, the loop or bend 58 merges directly into the end portion 41 (FIG. 2) around the opening 40, whereas a plate portion 60 generally parallel to the line 56 is located between the loop or bend 54 and the end portion 39 around the opening 38. Thus, the loops or bends 54, 58 are positioned nearer to the opening 40 than to the opening 38. From the loop or bend 58 an arm 62 extends from the outermost portion of said loop approximately in parallelism to the line 56 towards the location of the opening 38. When the plate spring 36 is subjected to initial tension between the openings 38, 40, the lines of force will generally follow the loops or bends whereas the arm 62 disregarding the fixed end portion thereof, will be free from tensions.

The support surfaces 45 and 47 on the projections 44 and 46, respectively, extend in mutually parallel planes, but are displaced relatively from one another. Thus, the support surface 45 has a greater spacing from the bottom plane of the frame 42 than the support surface 47. The surface 45 is delimited towards the portion 60 of the spring 36 by an edge 64 forming an inclined angle to the line 56in a manner evident from FIG. 2. The parallel displacement between the support surfaces 45 and 47 and the inclined edge 64 are of essential importance for the angular motions performed by the arm 62. To bring about these angular motions, the pin 32 acts on the loop or bend 54 at its transition into the straight portion 60 at a point 66 located on or near the line 56. By exposing the plate spring 36 to a pressure of predetermined magnitude acting transversally to the plane thereof at the point 66, a changeover of said arm 62 is effected so that said arm whereas the spring otherwise is in a plane state, forms an angle to said plane of the plate spring, as is illustrated in FIG. 3. According to the invention, the transmission ratio is very high so as to cause the arm 62 with one pole contact or terminal 68 located at its outer end to move over a distance many times greater than the point 66.

The plate spring 36 forms part of an electrical system and to this purpose, the screw joint 48 outside of the casing part 12 is connected with the terminal 70 of a cable 72. Another cable 74 is connected with a screw joint 76 carrying an arm 78 of electrically conductive material. Said arm 78, however, is insulated from the frame 42 and the plate spring 36. The arm 78 is provided with a pole of contact or terminal 80, the position of which relative the frame 42 and therewith relative the spring 36 is adjustable by providing an insulating body 82 formed with a groove 84 slightly above the center of said body. Depending on the degree to which the screw joint 76 is tightened, the insulating body 82 will compress the groove 84 to a larger or smaller degree and as a consequence thereof the pole of contact 80 of the arm 78 will have a variable spacing from the plane of the plate spring 36. As will be seen from FIG. 3, the pole 80 shall be located adjacent the plate spring so that the arm 62 when in the starting position being located substantially in the plane of the plate spring, establishes contact with the pole 80.

On the opposite side, the arm 62 cooperates with the end portion 86 of a set screw 88 screwed into a sleeve 90 which in turn is secured in the frame 42. The set screw 88 is operable from outside by means of a hand wheel or nob 92 or similar member. A cable 94 may be in electricity conductive connection with the set screw 88.

OPERATION The control device operates in the following manner. It be assumed that it has to control the water level between a predetermined low level A and a predetermined high level B. It be assumed further the operating condition at some moment is such that a pump actuated by the control device has been stopped after the lower value A had been reached. Thereafter, the water level rises continuously but is assumed not to have reached the value B. Under this condition, the plate spring 36 takes the position evident especially from FIG. 3. The arm 62 forms a great angle with the plane of the plate and abuts against the end portion or the shoulder 86 of the screw 88. In this case, the cable 94 has no connection for which reason no current passes through the control device.

The rising water level causes the pressure gradually to be increased within the chamber 20, due to which increase the membrane 16 forces the pin 32 towards point 66 on the plate spring 36. Said plate spring 36 exerts, however, a strong counter-pressure, and not until the high value B of the water level has been reached, is a snap-like change-over of the spring effected so that its arm 62 instead abuts against the pole or terminal on the arm 78. Now, the current circuit is closed from the cable 72 through the spring 36, the arm 78 and the cable 74 so that the pump is forced to start. In this position of the arm 62, only a little force is required to retain the arm in abutment against the pole 80. Since now the pump is in operation, the water level will fall and therewith also the pressure within the chamber 20, but the arm 62 remains in contact with the pole 80. This operating condition is continued until the low water level A has been reached and it will at that moment be possible for the spring 36 to preponderate and to cause the arm 62 to return to the shoulder 86 and thereby to interrupt the supply of current. This cycle is thereafter repeated in the same manner when the water again has risen to the level B.

To the same degree as the end portion 86 by tightening of the screw 88 is brought nearer to the plane of the plate spring 36, the force required for overcoming the resistance of the spring is reduced, i.e., the control device reacts for a lower maximum of pressure within the chamber 20. According to the invention, the control device can be adjusted by actuation of the hand-wheel or nob 92 for highest limit values of pressure within a wide scope whereas the holding pressure i.e. the pressure causing the arm 62 to be in contact with the pole 80 is substantially lower and in addition always constant or approximately constant.

It will be understood that the control device of the invention is also applicable to two-polar interrruption e.g. when reversing a motor for attaining a predetermined control cycle. In this case, the cable 94 is switched in, so that a current circuit is closed also when the arm 62 rests on the shoulder 86. The idea of the invention is applicable to other processings also when the unit, the magnitude of which is to be controlled, is represented by heat, motion of a body, speed of flow of a fluid etc.

While one more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

What is claimed is l. A control device comprising a reciprocable member, means for applying fluid pressure against one side of said member to move said member in one direction, a plate spring member, means for clamping said plate spring member adjacent its two ends under tension,

said plate spring member having a flexible arm integral therewith and projecting from one side thereof, a pair of stops positioned at opposite sides, respectively, of the plane of said plate spring member to be engaged, respectively, by said arm at opposite limits of angular movement of said arm, said plate being normally positioned nearer one of said stops than the other, so that said arm is required to move a greater distance to abut against said other stop than against said one stop, a pin secured to said reciprocable member to be reciprocable therewith, and positioned to engage said plate spring member transversely of the plane of said spring member between the clamped ends thereof, and operative upon predetermined movement of said reciprocable member in said one direction under predetermined pressure to flex said arm and snap it from its normal poi n insen asment with, a s 1h tonimo a ment with said one stop, the flexure of said arm caus-- ing it to remain in contact with said one stop until the pressure on said reciprocable member has fallen to a ment with said one stop. 

1. A control device comprising a reciprocable member, means for applying fluid pressure against one side of said member to move said member in one direction, a plate spring member, means for clamping said plate spring member adjacent its two ends under tension, said plate spring member having a flexible arm integral therewith and projecting from one side thereof, a pair of stops positioned at opposite sides, respectively, of the plane of said plate spring member to be engaged, respectively, by said arm at opposite limits of angular movement of said arm, said plate being normally positioned nearer one of said stops than the other, so that said arm is required to move a greater distance to abut against said other stop than against said one stop, a pin secured to said reciprocable member to be reciprocable therewith, and positioned to engage said plate spring member transversely of the plane of said spring member between the clamped ends thereof, and operative upon predetermined movement of said reciprocable member in said one direction under predetermined pressure to flex said arm and snap it from its normal position in engagment with said other stop into engagement with said one stop, the flexure of said arms causing it to remain in contact with said one stop until the pressure on said reciprocable member has fallen to a predetermined relatively low value whereupon said arm will return into engagement with said other stop, and means for adjusting said other stop to vary the magnitude of the angular movement required of said arm to engage said other stop, and wherein said clamping means secure said plate spring member to plane support surfaces which are parallel to one another but displaced from one another in said one direction, one of said surfaces has an edge inclined relative to said connecting line, and said said plate spring member bears on said edge when said arm moves into engagement with said one stop. 